Method for producing hollow rubber articles



- April 11, 1944. c, KEMPTQHORN 2,346,634

METHOD FOR PRODUCING HOLLOW RUBBER ARTICLES Filed July 15, 1942 2 Sheets-Sheet l INVENTOR. I

Davzd C.Kempihom April 11, 1944. D. c. KEMPTHORN METHOD FOR PRODUCING HOLLOW RUBBER ARTICLES 2 Sheets-Sheet 2 Filed July 15, 1942 INVENTOR. David C. Kempfhom Patented Apr. ii, 1944 E S PAT E 1-.

David C. Kempthorn, Akron, Ohio, assignor to The Sun Rubber Company, Barber-ton, Ohio, a

corporation of Ohio Application July 15, 1942, SerlalNo. 450,954 2 Claims. (Cl. 18-56) This invention relates to hollow rubber or like articles, such as hollow rubber character dolls, and to apparatus and methods for producing the same.

In the past hollow rubber articles of the character described have been produced by various so-called blowlng" methods by which usually a preformed hollow biscuit" was placed in a sectional vulcanizing mold and subjected to internal pressure to expand the wall of the biscuit against the surface of the mold cavity. The difficulty, however, has been that'this internal pressure forced the rubber between the parting surfaces of the mold sections to produce a flash or rind of excess rubber, which was required to be removed by separate trimming or buftlng operations.

One object of this invention is to provide a method and apparatus for vulcanizing hollow rubber or like articles, without substantial flash or rind along the parting line thereof caused by rubber flowing between the parting surfaces of the usual sectional molds.

This and other objects of the invention will be manifest from the following brief description and the accompanying drawings.

Of the accompanying drawings:

Figure 1 is a fragmentary view of a vulcanizing press, partly broken away, illustrating a cross-section through a rubber doll mold, prior to a vulcanizing cycle.

Figure 2 is a similar cross-section through a doll mold, but after vulcanization.

Figure 3 is an enlarged fragmentary cross-seetion at the parting line between the mold sec-' tions.

Figure 4 is a side elevation of a hollow rubber character doll, manufactured in accordance with the invention, partly brokenaway and in section through the integral noise-making-device.

Referring particularly to Figures 1. 2 and 3 of the drawings, the numerals l and H designate upper and lower platens of a vulcanizing press of known type in which the platens are relatively movable toward and from each I other. Mounted on the platens l0 and H are upper and lower mold sections l2, l2 and l3, l3, respectively,

of a plurality of cavity molds I4, M, the mold sections being adapted to register for vulc'anizing articles in the molds when the press is closed. The contour of the parting surface of molds M conforms generally to the outline of the articles produced therein, and the normalclearanoe between said surfaces is utilized for venting the mold cavities, as will be understood by those skilled in the art.

Secured in a recess I5 in the lower mold section l3 of each mold It is a plug it having its inner surface substantially flush with the inner surface of the mold cavity, and projecting inwardly of the plug may be a pin or core I! formed with an ovate or annular enlargement E8, in spaced relation to said inner surface of the cavity to provide a relatively short constricted neck portion IS. A relatively thin, annular enlargement 2!] may be provided on the pins in inwardly spaced relation to ovate portion N to provide an annular recess 2| of suitable depth, for 'purposes subsequently to be described. An inner end portion 22 of the pin ll is tapered inwardly to a point for piercing articles formed in the mold in a manner which will also be described later.

Extending through the plug l6 and pin I! is a passage 23 which communicates, through apertures 23 23 at the inner end of the pin, with the interior of the mold M, the outer end of the plug l6 being threaded into a conduit. 24 connected with a suitable source of supply (not shown) from which pressure fluid, such as steam, compressed air, hot water, etc., may be supplied to the interior of the mold cavity through said passage 23 to form an article in the mold under the influence of vulcanizing heat. The same connections maybe similarly utilized to apply suction within the mold, or within an article in the mold to vvent the same. The other molds in the press are similarly connected to the supply conduit 24.

In the operation of the apparatus, while the press is open hollow biscuits or casings B, roughly preformed from sheets of unvulcanized rubber in a known manner, are placed in the cavities of the lower mold sections, whereby the pin being hot from previous vulcanizing operations will pierce the lower wall portions of the biscuit and said wall portions will drape around the pin I 1 including the enlarged portions l8 and 20 thereof, substantially as illustrated in the lower part of Figure 1. The length of pin I1 is such that the draped portions of the walls of the biscuits will not close the apertures 23* from the passages 23. Upon placing the biscuits in the lower mold sections the press is operated to move the upper and lower mold sections into closed registering relation (see Figure 1).

In this closed position of the press, while the molds are maintained at vulcanizing temperature by suitable means (not shown), pressure fluid is supplied from the source of supply through conduit 23 to expand the walls of biscuits B against the surfaces of the mold cavities and thereby form the articles, as illustrated in Figure 2. It has been the practice in the past to apply substantially full vulcanizing pressure to the interior of the biscuit upon closing the press, whereby the heat of the mold caused the rubber to soften immediately and flow under the internal pressure into the spaces between the parting surfaces of the mold sections, thereby forming considerable excess rubber known as flash" or rind which was required to be removed by a separate trimming or bufllng operation after vulcanization. In accordance with the present invention the initial pressure supplied to the interior of the biscuits may be relatively low, say approximately ten pounds per square inch, whereby the walls of the biscuits B are expanded against the mold cavities with'insuificient pressure to force the rubber between the parting surfaces of the mold sections to a material degree, this low pressure being maintained a sufllcient length of time, as for example about 1 minutes, according to temperature conditions, to permit the heated molds to form a skin coat on the articles being formed from the biscuits, after which full vulcanizing pressure may be supplied through conduit 24 for the completion of the curing cycle. The skin coating or hardened outer surfaces formed on the articles, particularly along the parting lines thereof, will prevent substantial penetration of the rubber between the parting surfaces of the mold sections when full pressure is applied, thereby obviating the usual necessity of trimming excess or flash rubber at the parting line of the completed articles, or substantially reducing the labor usually required to remove such excess. Application of vulcanizing pressure within eac biscuit B together with the heat of vulcanization, to form an article, as described above, will cause rubber of the wall of the biscuit to flow about the pin I I, substantially as shown in Figure 2, thereby forming a noise-making device integral with the wall of the finished article (see Figure 4). A chamber 25 is provided in the device by the enlargement iii of pin l1, and spaced outer and inner, centrally apertured, walls or diaphragms 26 and 21 of the chamber are provided by rubber forming around the constricted portion l9 and-the reduced portion or annular groove 2!, respectively. A certain amount of excess rubber may flow inwardly over the annular enlargement 20 to form a. second chamber, but even though there should not be sufficient rubber to form a uniformly shaped inner portion of the device, the

arrangement may be such that there willalways be sufficient rubber to form the inner diaphragm 21 in a uniform manner, whereby the noise-making propensities of articles produced as described in the molds M will be substantially uniform. When the vulcanizing cycle is completed fluid pressure to the interior of the articles formed in the molds may be cut off and suction applied, through conduit 24 and the passage 23, to vent the article, thereby to permit the vulcanizing press to be opened immediately at the end of the curing cycle for removal of the articles.

An article produced as described above is shown in Figure 4. Depressing a portion of this article and then releasing the same will cause a rush of air through chamber, thereby creating a squawking or whistling sound.

Modifications of the invention may be resorted to without departing form the spirit thereof or the scope of the appended claims.

What is claimed is:

1. A method of making hollow rubber articles comprising inserting a preformed hollow biscuit of unvulcanized rubber in sectional mold, applying relatively low pressure within the biscuit to expand the same against the surfaces of the mold cavity while the mold is hot, said low pressure being insufficient to-cause material flow of the' rubber between the parting surfaces of the mold due to the heat thereof, whereby the biscuit is partially cured with little or no flash, and increasing the pressure within the biscuit to complete curing the same under the influence of vulcanizing heat.

2. A method of making hollow rubber or like articles comprising partially vulcanizing a preformed hollow biscuit of unvulcanized rubber in a sectional mold while the internal pressure of the biscuit is maintained relatively low substantially to obviate fiow of rubber between the parting surfaces of the mold, and completing vulcanization of the biscuit while the internal pressure thereof is maintained relatively high,

DAVID C. KEMPTHORN. 

